Snow is a critical factor shaping the high mountain environments of western North America through its impacts on vegetation and alpine glaciers. Mountain snow also impacts distant lowland regions in the West through its role in generating the runoff and stream flow. Despite the importance of snow, long-term records (multiple decades or longer) of spatial and temporal variability in snowpack are lacking. Records that encompass a century or more are critical for understanding trends and cycles in snow climate, but these records do not currently exist. Long-term records are likewise essential as a baseline for evaluating recent and future climate change. This project uses tree-rings to reconstruct spatial variations in snowpack spanning several centuries or more for three key high-mountain areas: the Upper Colorado River Basin, Upper Yellowstone/Missouri River Basin, and the Columbia and Saskatchewan River Headwaters. The resulting high-resolution maps of past snowpack will be used to understand how ocean sea surface temperatures (e.g., El Nino, Pacific Decadal Oscillation) influence snowpack in the West. This question is particularly important in sorting out the degree to which current trends are "natural" vs. trends resulting from human-caused changes in climate. Finally, this project will develop tools for water managers to assess how variability in snowpack affects options available for resource management. Although this research focuses on three distinct regions, the concepts and methodologies the investigators will develop will be applicable in similar settings throughout the world. The overarching goal of this project is to lay the foundation for snowpack reconstructions that encompass all the high mountain areas in western North America.
This project will provide invaluable information on the response of mountain environments to large-scale climatic variability and change. The long-duration records of snowpack provided in this and subsequent studies will be especially useful for understanding how the interaction of the ocean with the atmosphere influences climate over decadal and longer timescales. This work builds a foundation for understanding the past, present, and future dynamics of natural systems in mountain areas. This project provides critical information to water managers and other decision makers who are seeking to assess the long-term sustainability of water resources in western North America.
